Tire antenna containment system and method

ABSTRACT

An antenna system and method for tire monitoring systems provides a tubular antenna housing composed of suitably flexible material. An antenna is placed within the housing in either a straight configuration or a preferred alternative shape such as sinusoidal. The tubular housing may be straight walled or corrugated for additional flexibility. The electronics package may be provided with opposite ends dimensioned and configured for mating engagement with opposite ends of the antenna tube. Mating engagement between the electronics housing ends and the antenna tube ends secure the antenna tube to the electronics package. Subsequently, the antenna system may be secured by adhesive or other known techniques to the tire inner liner.

FIELD OF THE INVENTION

The invention relates generally to an apparatus, including an antennaand a transponder, for a tire pressure monitoring system and, morespecifically, to a tire antenna containment system and method for a tirepressure monitoring system.

BACKGROUND OF THE INVENTION

It is common to employ annular apparatus, including an antenna, forelectronically transmitting tire or wheel identification or other dataat radio frequency. The apparatus includes a radio-frequency transpondercomprising an integrated circuit chip having data capacity at leastsufficient to retain identification information for the tire or wheel.Other data, such as the inflation pressure of the tire or thetemperature of the tire or wheel at the transponder location, can betransmitted by the transponder along with the identification data.

It is known in the art to employ an annular antenna to transmit, atradio frequencies, data from a transponder contained within thestructure of a tire or tire and wheel assembly. The antenna comprises awire or strands of wire formed into a loop that may be sheathed in anextruded covering formed from a suitable material such as plastic. Theplastic sheath in combination with the antenna form a unitary body thatmay be affixed to a green tire in a pre-build assembly process orattached to a finished tire in a post-cure operation. While the antennaand transponder may be incorporated into a tire during “pre-cure”manufacture, in practice it is very difficult to do this. Both radialply and bias ply tires undergo a substantial diametric enlargementduring the course of manufacture. Bias ply tires are expandeddiametrically when inserted into a curing press, which typically has abladder that forces the green tire into the toroidal shape of the moldenclosing it. Radial ply tires undergo diametric expansion during thetire building or shaping process and a further diametric expansionduring the course of curing. Any annular antenna and the electroniccircuitry associated therewith built into the tire must be able tomaintain structural integrity and the mechanical connection between theantenna and transponder package during the diametric enlargement of thetire during its manufacture. Once assembled into the tire, any detectedmalfunction in the antenna, transponder, or antenna to transponderconnection that cannot be repaired destroys the utility of the tire andmay necessitate a scrapping of the tire. Hence, placement of an annularantenna-transponder assembly into a tire during its manufacture carriesrisk that subsequent failure or breakage of assembly components willnecessitate the destruction of the otherwise suitable host tire.

Not only is the risk of damage to an annular antenna-transponder systempresent during its incorporation into a tire during manufacture, butdamage to such systems are not uncommon from operation of the tire on avehicle. Loop antennas and the electronics associated therewith aresubjected to substantial compressive strain and at the sidewall a highstrain amplitude. Such locations represent high load and deformation toregions of the tire. Consequently, antenna, transponders, and theconnections therebetween in such locations are prone to breakage andmechanical or electrical failure.

In order to protect the electronics from undergoing the rigors of a tirecure cycle, it has been proposed that the annular antenna apparatus beapplied to a tire in a post-cure operation. The antenna assembly isformed by extruding rubber over an antenna into a specific shape,typically annular, and then the antenna assembly is cured. The antenna,in the cured composite, may then be threaded through an electronicpackage. Finally, the rubber composite and electronics package is overcured with rubber. The annular antenna assembly may then be glued as afinished unit to the inner side wall of a tire.

While working well, several shortcomings prevent such an antennaassembly and assembly procedure from representing an ideal solution tothe needs of the industry. First, sheathing the antenna wire(s) withinan elastic sheath, while protecting the antenna, may not allowsufficient freedom of movement in the antenna loop. Such restrictionagainst antenna elongation can cause antenna breakage over time.Secondly, the steps of attaching the electronics package to the antennawire(s) and over molding the electronics package in a secondary stepadds complexity and labor to the antenna apparatus assembly procedure,increasing assembly time and undesirably adding to the cost of theresultant tire.

There is, accordingly, a continuing need for an antenna apparatus andattachment procedure for easily and efficiently incorporating theassembly into a tire. Such a procedure preferably applies the antennaassembly to an electronics package in a post-cure procedure in order toprotect the electronics from the rigors of a tire curing cycle. Theantenna apparatus must provide sufficient structural integrity towithstand the stresses attendant use in a vehicle-mounted tire andprotect the structural integrity of the antenna in such an environment.Moreover, the antenna apparatus ideally will maintain the antenna in itsoptimal, intended configuration and shape during the tire's life. Sincethe performance of the tire pressure monitoring system is dependent uponeffective communication between the tire electronics and a remote readervia the antenna, maintaining the antenna in an optimal configuration ishighly desirable. Additionally, the desired antenna assembly and methodof assembly will provide a means for interconnecting the antenna cablean electronics package in a post-cure procedure that is both costeffective and reliable.

SUMMARY OF THE INVENTION

The subject invention overcomes the deficiencies in known antennasystems and methods for tire monitoring systems by providing a tubularantenna housing composed of suitably flexible material. An antenna isplaced within the housing in either a straight configuration or,preferably, a sinusoidal, helical, or zigzag shape. The tubular housingmay be straight walled or corrugated for additional flexibility. Thetubular housing thus serves to protect the antenna from corrosive gasesand moisture in the tire cavity while allowing the antenna to flex andextend without restriction. In one aspect of the invention, theelectronics package may be provided with opposite ends dimensioned andconfigure for mating engagement with opposite ends of the antenna tube.The electronics housing ends once mated with ends of the tube secure theattachment of the antenna tube to the electronics package. Subsequently,the antenna system may be glued into or otherwise attached to the tirecavity in conventional fashion. The method of assembly thus includes thesteps: positioning an elongate antenna cable into a tubular antennahousing, the housing having a central axial bore open at opposite ends;housing electronics within a package having opposite ends shaped anddimensioned for mating engagement with the tube opposite ends;connecting ends of the antenna cable to the electronics housed withinthe package; and mateably attaching the package ends to the antenna tubeends to attach the antenna housing to the electronics package.

The advantages of the invention, which will be apparent to those skilledin the art, are achieved by preferred and alternative embodiments thatare described in detail below and illustrated by the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tire and the subject annular apparatuswith portions of the tire removed for the purpose of illustration.

FIG. 2 is an enlarged partially exploded perspective view of a portionof the antenna tube assembly and the electronics package.

FIG. 3 is a side elevation view thereof shown partially in section forillustration.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A tire pressure monitoring system typically consists of a transponderhaving one or more sensors. The transponder and associated electronicsare housed within a package. In order to send or receive RF signals, atransponder must have an antenna. The antenna is preferably annular inconfiguration in the subject invention but may have alternative shapesif desired. The antenna may either be incorporated into the tire duringmanufacture or affixed to the tire by way of a post manufactureprocedure. As used herein, an “annular antenna” may be circular, oblong,symmetrical, or asymmetrical without departing from the subjectinventive principles. However, the preferred configuration of theantenna is circular and sized to overlap the tire sidewall region towhich it attaches. Other locations such as upper side wall or tire crownarea are also possible for assembly location. The antenna may comprise asingle wire or a plurality of strands. Various commercially availabletransponders, sensors, and other electrical devices deployed incombination with an annular antenna formed from conventional conductivematerials are suitable for use in conformance with the principles of thesubject invention.

Acceptable materials for the antenna wire include steel, aluminum,copper, copper alloys or other electrically conducting wire. Asdisclosed in this patent document, the wire diameter is not generallyconsidered critical for operation as an antenna for a transponder. Fordurability, stranded steel wire consisting of multiple strands of finewire is preferred. Other wire options available include ribbon cable,ribbon conductors on fabric strands, flexible circuits, conductive film,conductive rubber, etc.

Referring initially to FIG. 1, a preferred embodiment 10 of the subjectinvention is shown deployed within a tire 12. The tire 12 is formed fromconventional materials such as rubber or rubber composites byconventional means and may comprise a radial ply or bias plyconfiguration. A typical tire 12 is configured having a tread 14, ashoulder 16, an annular sidewall 18, and a terminal bead 20. An innerliner 22 is formed and defines a tire cavity 24. The tire 12 is intendedfor mounted location upon an annular rim 26 having a peripheral rimflange and an outer rim flange surface 30. Rim 26 is conventionallyconfigured and composed of a suitably strong metal such as steel.

An annular antenna 32 is provided and, in the preferred embodiment,embodies a sinusoidal configuration. Antenna 32 may be alternativelyconfigured into alternative patterns or comprise a straight wire(s) ifdesired and may be filament wire, or cord or stranded wire. Acceptablematerials for the wire include steel, aluminum, copper, copper alloys orother electrically conducting wire. As mentioned previously, the wirediameter is not generally considered critical for operation as anantenna and multiple strands of fine wire is preferred. The curvilinear,or zigzag form of antenna 32 provides flexibility and minimizes the riskof breakage during manufacture and use explained below.

With continued reference to FIG. 1, a transponder module 34 of thegeneral type described above is provided and may include means forsensing tire parameters such as pressure and temperature. Included aspart of the apparatus 10 is a containment tube 36 formed preferably butnot necessarily into the annular configuration shown. Containment tube36 is formed of electrically insulating, elastic material as will bedescribed below. In the post manufacturing state, therefore, theapparatus 10 comprising antenna 32, transponder module 34, andcontainment tube 36, in a unitary, generally circular, assembly that isreadily transportable and handled for attachment to tire 12. Thediameter of the apparatus assembly 10 is a function of the size of thetire 12 and the preferred attachment location thereon.

In combined reference to FIG. 1, the apparatus 10 is affixed to liner 22of the tire 12 preferably in a post-manufacture assembly operation.Attachment may be by means of an adhesive or other known conventionalmeans of affixing a device to a rubber composite.

With reference to FIGS. 2 and 3, pursuant to the invention, annularcontainment tube 36 houses the antenna 32 therein preferably, but notnecessarily, in a loose fashion. The tube 36 is composed preferably ofelasticized fibers such as Spandex, rubber, vinyl, or may be composed ofother material compositions having sufficient flex characteristics. Theantenna cable 32 may be either a single wire or a strand of pluralwires.

When situated in a tire and subjected to stresses present within thetire, the tube 36 so composed will flex and elongate from an initialrelaxed state into an extended state. The wavy, sinusoidal, or zigzagshape of the antenna 32 will straighten and flex within the tube toaccommodate the elongation. When released from the influence of tirestress, the tube will recover and contract to the original, optimal,tube shape. The tube 36 may be externally configured having a straightwall or be corrugated for additional flexibility (not shown).

As will be appreciated from FIGS. 2 and 3, the electronics package 34houses electronics of a type commercially available and in common use.The electronics may include one or more sensors for monitoring theinternal tire condition and interconnection means for connecting withthe antenna 34. The ends of the antenna 32, for example, may be solderedto terminals within the package 34 to provide means for transmittinginput and output signals between the sensor package and an externalreader (not shown). The package 34 includes a base housing 38 ofgenerally, but not necessarily, cylindrical configuration having anaccess axial bore 40 extending therethrough. Bore 40 extends intoopposite ends 42, 44 of the housing 38 and represents access to internalelectronics housed within housing 34.

The ends 42, 44 of the housing may be configured as protrusions ornipples extending from the housing 38 in one aspect of the invention.Alternatively, the ends 42, 44 may be coplanar with the sides of housing34 if so desired. The ends 42, 44 represent sockets having aconfiguration and inner diameter for receiving opposite ends of the tube36 therein. Alternatively, the ends 42, 44 and tube 36 may be configuredsuch that ends 42, 44 are received within the ends of tube 36. In theembodiment shown, ends of the tube 36 are press fit within the ends 42,44 of housing 38. Adhesives may be applied to external surfaces of thetube ends to retain the tube in a mating engagement with housing 38. Anannular recess 46 may be formed within each housing end 42, 44positioned to receive a complementary annular shoulder 48 formed toproject from each end of the tube 36 if desired. Engagement of theshoulder 48 with the recess 46 mechanically couples the tube to thehousing 38.

The method of assembly the tube 36 to housing 38 and electricallyconnecting antenna 32 to the electronics within housing 34 is thusstraight forward and efficient. The method of assembly includes thesteps: positioning the elongate antenna cable 32 into the tube 36preferably in a loose fit, the tube 36 having a central axial bore openat opposite ends; housing electronics within a package 34 havingopposite ends 42,44 shaped and dimensioned for mating engagement withthe tube opposite ends; connecting ends of the antenna cable 32 to theelectronics housed within the package; and mateably attaching thepackage ends to the antenna tube ends to attach the antenna housing tothe electronics package.

From the foregoing, it will be appreciated that the subject inventionsatisfies the need of the industry for a convenient, reliable method ofaffixing an antenna in annular form to the inside of a tire. Use of anelasticized textile material, rubber, vinyl, or similar in the formationof the tube 36 creates a containment that protects and maintains theantenna housed therein in an optimal configuration. Tube 36 iseconomical to produce and highly effective. The tube extends from aninitial relaxed state when the stresses within a tire are imposed; thematerial of the tube and the curvilinear configuration of the antennaaccommodating such an elongation. The recovery of the tube to itsoriginal form is predictable, and durable enough to withstand thenecessary number of elongation/recovery cycles within a typical tireused in an intended manner. LYCRA SPANDEX (registered trademark of E.I.DuPont de Nemours & Company), for example, is one material that may beemployed. Other commercially available stretch fabrics may also beutilized. Such fabrics are available having a selection of stretchresistance, stress decay, hysteresis, residual stretch, and recoverycharacteristics. Materials will generally have a cycle limit,representing the greatest elongation to which the material may besubjected without resulting in a permanent deformation. The holdingpower and stretch resistance may further be selected to provide anoptimum match between the elasticized characteristics of the tube 36 andthe magnitude of elongation resulting from stresses a tire environment.

The advantages of the subject invention over antenna apparatus composedof a rubber carrier strip are significant. Spandex fiber, rubber andvinyl tube construction can be stretched repeatedly and still recover tovery near original length and strength; the material may be stretchedthrough a high number of cycles without breaking; the material isstronger, more durable and exhibits a higher retractive force.

While the above sets forth a preferred embodiment and alternativeembodiments of the subject invention, the invention is not intended tobe so limited. Other embodiments that will be apparent to those skilledin the art and which utilize the teachings herein set forth, areintended to be within the scope and spirit of the present invention.

1. An apparatus for a tire comprising: an elongate antenna; an elongatetubular antenna housing composed of suitably flexible material andhaving an axial bore loosely receiving the elongate antenna therein andextending between opposite antenna housing ends; an electronics packagehaving outward ends dimensioned and configured for mating engagementwith opposite antenna housing ends, whereby attaching the antennahousing to the electronics package.
 2. An apparatus according to claim 1wherein the antenna has a non-linear configuration.
 3. An apparatusaccording to claim 1 wherein antenna housing includes a substantiallystraight walled external segment.
 4. An apparatus according to claim 1wherein the antenna housing includes a substantially corrugated wallexternal segment.
 5. An apparatus according to claim 1 wherein theantenna is loosely contained surrounded by air within the antennahousing axial bore.
 6. An apparatus according to claim 1 wherein theelectronics package ends include retention means for engaging theantenna housing ends.
 7. An apparatus according to claim 6 wherein theretention means comprises at least one shoulder engaging an inner wallof the antenna housing within the axial bore.
 8. A tire having anantenna assembly incorporated therein, the tire comprising: a tire bodyhaving an inward facing wall; an elongate antenna; an elongate tubularantenna housing attached to the tire body inward wall, the antennahousing being composed of flexible material and having an axial boreloosely receiving the elongate antenna and extending between oppositeantenna housing end openings; an electronics package having outwardopposite ends for mating engagement with opposite antenna housing endsrespectively, whereby attaching the antenna housing to the electronicspackage.
 9. A tire according to claim 8 wherein the antenna has anon-linear configuration.
 10. A tire according to claim 8 wherein theantenna housing includes a substantially straight walled externalsegment.
 11. A tire according to claim 8 wherein the antenna housingincludes a substantially corrugated wall external segment.
 12. A tireaccording to claim 8 wherein the antenna is loosely contained within theantenna housing axial bore surrounded by air.
 13. A tire according toclaim 8 wherein the electronics package ends include retention means forengaging the antenna housing ends.
 14. A method for mounting an annularantenna and transponder to a tire, comprising the steps: providing anelongate antenna having opposite ends; housing the antenna looselywithin an axial bore of an elongate tubular antenna housing, the axialbore terminating at opposite antenna housing ends; terminating theopposite ends of the antenna to electronics housed with a housing havingopposite ends; placing the electronics package ends into matingengagement with the opposite antenna housing ends to affix the antennahousing to the electronics package housing.
 15. A method of assemblyaccording to claim 14 further comprising the step of forming the antennainto a non-linear configuration.
 16. A method of assembly according toclaim 14 further comprising the step of forming the antenna and theantenna housing into an annular configuration.